Method and apparatus for concurrent welding and excise of battery separator

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 11/126,943, filed May 11, 2005 now U.S. Pat. No. 7,718,027, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This disclosure relates generally to self-contained energy sources, and more particularly to method and apparatus for concurrent welding and excise of battery separator.

BACKGROUND

Energy storage components, such as batteries and capacitors, are used in a variety of electronic devices. As technology evolves, devices using these components consistently demand smaller component sizes. However, in meeting the demands of technology, these components cannot sacrifice performance. As such, the art requires energy storage components which are smaller, but which meet or exceed energy requirements.

In meeting these requirements, manufacturing improvements are needed. New manufacturing processes must manage new components efficiently, and reliably, enabling new configurations. To improve space efficiency, new manufacturing processes are needed to tailor components to their respective application. Hand tailoring of components, such as flexible sheets, can be labor intensive and time consuming. Thus a new automated system is needed which can efficiently tailor components for use. Further, what is needed is a tailoring system which is more reliable than hand tailoring.

SUMMARY

The above-mentioned problems and others not expressly discussed herein are addressed by the present subject matter and will be understood by reading and studying this specification.

One embodiment of the present subject matter relates to a method which includes positioning a bottom and top polymeric separator sheet on a working surface, with a substantially planar battery anode disposed therebetween; positioning a cutting and welding tool against the top polymeric sheet, the cutting and welding tool having an elongate surface with a protrusion extending away from the elongate surface and along the elongate surface, the elongate surface shaped for positioning offset from and outside of the perimeter of the substantially planar battery anode; applying a pressure and an electrical current to the cutting and welding tool such that top and bottom polymeric separator sheets are welded into a bag and such that the bag is excised from the top and bottom separator sheets, with the substantially planar battery anode disposed in the bag; stacking the substantially planar battery anode and at least one cathode into a battery stack; and disposing the battery stack into a battery case having at least one feedthrough, with a first terminal connected to the battery stack through the at least one feedthrough, and with the battery case filled with an electrolyte, wherein the protrusion is defined by laser cutting the cutting and welding tool.

Additionally, in one embodiment, the present subject matter relates to a method which includes positioning a bottom and top polymeric separator sheet on a working surface, with a substantially planar battery anode disposed therebetween; positioning a cutting and welding tool against the top polymeric sheet, the cutting and welding tool having an elongate surface with a protrusion extending away from the elongate surface and along the elongate surface, the elongate surface shaped for positioning offset from and outside of the perimeter of the substantially planar battery anode; applying a pressure and an electrical current to the cutting and welding tool such that top and bottom polymeric separator sheets are welded into a bag and such that the bag is excised from the top and bottom separator sheets, with the substantially planar battery anode disposed in the bag; stacking the substantially planar battery anode and at least one cathode into a battery stack; and disposing the battery stack into a battery case having at least one feedthrough, with a first terminal connected to the battery stack through the at least one feedthrough, and with the battery case filled with an electrolyte, wherein the protrusion is defined by machining the cutting and welding tool.

One embodiment of the present subject matter relates to a method which includes positioning a bottom and top polymeric separator sheet on a working surface, with a substantially planar battery anode disposed therebetween; positioning a cutting and welding tool against the top polymeric sheet, the cutting and welding tool having an elongate surface with a protrusion extending away from the elongate surface and along the elongate surface, the elongate surface shaped for positioning offset from and outside of the perimeter of the substantially planar battery anode; applying a pressure and an electrical current to the cutting and welding tool such that top and bottom polymeric separator sheets are welded into a bag and such that the bag is excised from the top and bottom separator sheets, with the substantially planar battery anode disposed in the bag; stacking the substantially planar battery anode and at least one cathode into a battery stack; and disposing the battery stack into a battery case having at least one feedthrough, with a first terminal connected to the battery stack through the at least one feedthrough, and with the battery case filled with an electrolyte, wherein the protrusion is defined by photochemical etching the cutting and welding tool.

This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1A</figref> is a front view of a system schematic for welding and cutting power source components, according to one embodiment of the present subject matter.

<figref idref="DRAWINGS">FIG. 1B</figref> is a front view of a system schematic for welding and cutting power source components, according to one embodiment of the present subject matter.

<figref idref="DRAWINGS">FIG. 2</figref> is a partial bottom view of a cutting and welding tool, according to one embodiment of the present subject matter.

<figref idref="DRAWINGS">FIG. 3</figref> is a cross section taken at line “<b>3</b>” of <figref idref="DRAWINGS">FIG. 2</figref>, according to one embodiment of the present subject matter.

<figref idref="DRAWINGS">FIG. 4</figref> is a cross section of a cutting and welding tool, according to one embodiment of the present subject matter.

<figref idref="DRAWINGS">FIG. 5A</figref> shows a top and bottom separator sheet and a cross section of a cutting and welding tool, according to one embodiment of the present subject matter.

<figref idref="DRAWINGS">FIG. 5B</figref> shows a welded top and bottom separator sheet, a cross section of a cutting and welding tool, and scrap, according to one embodiment of the present subject matter.

<figref idref="DRAWINGS">FIG. 6</figref> is a method for cutting and welding separator sheets, according to one embodiment of the present subject matter.

DETAILED DESCRIPTION

The following detailed description of the present subject matter refers to subject matter in the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. References to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is demonstrative and not to be taken in a limiting sense. The scope of the present subject matter is defined by the appended claims, along with the full scope of legal equivalents to which such claims are entitled.

Self-powered electronic devices are known. For example, self-powered implantable medical devices are now in use for treating a variety of diseases. Implantable pulse generation devices, as well as other types of implantable medical devices, are powered by a battery contained within the housing of the device, in various embodiments. The present subject matter discusses batteries suitable for use in implantable medical devices, as well as other devices requiring self-contained power.

Batteries include various subcomponents. For example, various battery embodiments include opposing anode and cathode plates. These electrode subcomponents, in various embodiments, are isolated by separator. In various embodiments, separator is porous to accommodate electrolyte adapted to sustain ionic transfer between the electrodes. In additional embodiments, the separator includes failsafe subcomponents intended to decrease breakdown by reducing or eliminating ionic transfer. For example, some embodiments include a meltable separator. Various separator embodiments include three layers of porous separator material, such that the center material melts and clogs the pores of the external layers, reducing or eliminating ionic transfer. To ensure that ionic transfer between the anode and the cathode is reduced, in some embodiments, the present subject matter includes separator bags enveloping the battery anode. Bag embodiments cover a large amount of ionic paths between anodes and cathodes. The present subject matter relates to construction of these bags, in various embodiments.

<figref idref="DRAWINGS">FIG. 1A</figref> is a front view of a system schematic for welding and cutting power source components, according to one embodiment of the present subject matter. In various embodiments, the system includes a cutting and welding tool <b>108</b>, and a stack having a top polymeric separator sheet <b>104</b>, an anode <b>106</b>, and a bottom separator sheet <b>102</b>. Although this embodiment includes an anode, other embodiments can include a cathode. In various embodiments, the bottom <b>102</b> and top <b>104</b> polymeric sheets include a microporous membrane having a polyethylene layer disposed between two polypropylene layers. Various embodiments include sheets available under the brand name CELGARD, a product of Celgard LLC, of Charlotte, N.C. 28273. Other sheets including additional materials, however, are included within the scope of the present subject matter.

In various embodiments, the battery anode includes lithium. The battery electrode, when viewed from the top, may have any shape, including rectangular shapes, circular shapes, or irregular shapes. Both the shape of the cross section and the top view profile shape of the electrode are provided for explanation, but other shapes are possible. In cathode embodiments, the cathodes include manganese dioxide.

The stack rests on a working surface <b>110</b>, in various embodiments. The illustration shows that the cutting and welding tool is incident unto the stack. In various embodiments, the present subject matter includes positioning a cutting and welding tool <b>108</b> against the top polymeric sheet <b>104</b>. In alternate embodiments, the cutting and welding tool is fixed to a first static working surface, and a second working surface sandwiches the top and bottom polymeric separator layers and anode between the cutting and welding tool and the second working surface. Additional fixtures are within the scope of the present subject matter.

<figref idref="DRAWINGS">FIG. 1B</figref> is a front view of a system schematic for welding and cutting power source components, according to one embodiment of the present subject matter. The illustration shows components after processing with the cutting and welding tool <b>108</b>. The illustration shows an anode welded between bottom <b>102</b> and top <b>104</b> polymeric separator sheets. The components rest on working surface <b>110</b>. Scrap materials <b>112</b>, from which the top and bottom separator layers are separated, are also illustrated.

In various embodiments, the cutting and welding tool <b>108</b> has an elongate surface with a protrusion extending away from the elongate surface and along the elongate surface. <figref idref="DRAWINGS">FIG. 2</figref> is a partial bottom view of a cutting and welding tool <b>108</b>, taken at line “<b>2</b>” of <figref idref="DRAWINGS">FIG. 1</figref>, according to one embodiment of the present subject matter. Visible in the figure is a mounting eyelet <b>202</b>. Visible are the elongate surface <b>204</b> and the protrusion <b>206</b>. In various embodiments, the cutting and welding tool <b>108</b> is a thin ribbon-shaped band. In some embodiments, the cutting and welding tool <b>108</b> is substantially rigid. In various embodiments, the cutting and welding tool <b>108</b> is metallic.

<figref idref="DRAWINGS">FIG. 3</figref> is a cross section taken at line “<b>3</b>” of <figref idref="DRAWINGS">FIG. 2</figref>, according to one embodiment of the present subject matter. Illustrated are the protrusion <b>206</b> and the elongate surface <b>204</b> of the cutting tool <b>108</b>. In various embodiments, the protrusion is rectangular when viewed from a cross section. <figref idref="DRAWINGS">FIG. 4</figref> is a cross section of a cutting and welding tool, according to one embodiment of the present subject matter. <figref idref="DRAWINGS">FIG. 4</figref> demonstrates that the protrusion <b>406</b> has a triangular cross section, in various embodiments, bordered by elongate surface <b>404</b>. In various embodiments, the width of the protrusion is a fraction of the width of the ribbon.

Referring again to <figref idref="DRAWINGS">FIG. 2</figref>, in various embodiments, the cutting and welding tool <b>108</b> is shaped for positioning offset from and outside of the perimeter of the battery anode <b>210</b>. For example, when the anode is disposed between a top and bottom <b>102</b> sheet, the cutting surface is shaped such that it can press the sheets together by contacting the top sheet along an area around the anode <b>210</b>. Contact between the cutting and welding tool <b>108</b> and the top sheet occurs proximal the elongate surface <b>204</b> and the protrusion <b>206</b>. In various embodiments, an anode tab portion <b>209</b> of the battery anode extends outside the bag. Additional embodiments include alternate anode configurations and shapes also fall within the scope of the present subject matter.

Various embodiments of the present subject matter include applying a pressure and an electrical current to the cutting and welding tool <b>108</b> such that top and bottom <b>102</b> polymeric separator sheets are welded into a bag. For example, some embodiments define a weld extending around the battery anode proximal the elongate surface <b>204</b>. The weld may form a circuit around the anode, or may partially surround the anode, in various embodiments. In various embodiments, the battery anode is disposed in the bag. Various embodiments also excise the bag from the top and bottom separator sheets. In various embodiments, the excise occurs proximal protrusion <b>206</b>.

In various embodiments, the present subject matter uses a cutting and welding tool attached to a thermal impulse sealing fixture. One embodiment uses an HD-0 fixture manufactured by ALINE HEAT SEAL CORPORATION, of Cerritos, Calif. 90703. This fixture includes controllers manufactured by ROPEX of 74321 Bietigheim-Bissingen, Germany. Other fixtures and controllers are within the scope of the present subject matter. In various embodiments, the cutting and welding tool <b>108</b> is attached to a thermal impulse sealer at mounting eyelets <b>202</b>. The duration and intensity of the heat are variable depending on the application, in various embodiments. Additionally, pressure used by the machine is variable and dependent on an application, in various embodiments.

With regard to pressure, in various embodiments, the cutting and welding tool is subjected to a single force vector extending orthogonally into the top sheet. <figref idref="DRAWINGS">FIGS. 5A-5B</figref> show a top <b>104</b> and bottom <b>102</b> separator sheet and a cross section of a cutting and welding tool <b>108</b>, according to one embodiment of the present subject matter. In various embodiments, the cutting and welding tool subjects a varied pressure <b>502</b> (illustrated with vectors) on the top sheet <b>104</b> to which it is incident. The illustrated varied pressure <b>502</b> is for explanation only, and other pressure configurations are possible. Additionally, alternate force vector configurations are possible as well. The example illustrates a high pressure area proximal the protrusion <b>206</b>, and a lower pressure area proximal the elongate surface <b>204</b> of the cutting and welding tool <b>108</b>.

This variable pressure achieves various results. One result is that the low pressure areas are not cut. These areas are welded, in various embodiments. Another result is that an excise occurs proximal the protrusion <b>206</b>. An excised top and bottom sheet are illustrated in <figref idref="DRAWINGS">FIG. 5B</figref>. The illustration shows scrap <b>112</b>. Overall, in various embodiments, by heating the cutting and welding tool while providing a force input, a weld and excise are performed.

In various embodiments, because of the combination of pressure and heat energy for cutting and welding, the size and shape of the protrusion is important. As such, various methods are employed to control the distance the protrusion extends away from the elongate surface <b>204</b> of the cutting and welding tool <b>108</b>. In various embodiments, the protrusion is defined by laser cutting the cutting and welding tool. In additional embodiments, the protrusion is defined by machining the cutting and welding tool. In additional embodiments, the protrusion is defined by photochemical etching the cutting and welding tool.

<figref idref="DRAWINGS">FIG. 6</figref> is a method for cutting and welding separator sheets, according to one embodiment of the present subject matter. In various embodiments, the method includes positioning a bottom and top separator sheet on a working surface <b>602</b>, with a substantially planar anode disposed therebetween. Additionally, in various embodiments the method includes positioning a cutting tool against the top polymeric sheet <b>604</b>, the cutting tool having an elongate surface with a protrusion extending away from the elongate surface and along the elongate surface, the elongate surface shaped for positioning offset and outside the perimeter of the anode, wherein the protrusion is defined by laser cutting the cutting tool. In various embodiments the method includes applying a pressure and an electrical current to the cutting tool <b>606</b> such that top and bottom polymeric separator sheets are welded into a bag and such that the bag is excised from the top and bottom separator sheets, with the anode disposed in the bag. Some embodiments include stacking the anode and at least one cathode into a battery stack <b>608</b>. Additionally, some embodiments include disposing the battery stack into a battery case filled with an electrolyte <b>610</b>.

APPLICATION

In various embodiments, the present subject matter includes stacking a battery anode at least partially enveloped by a separator bag into a battery stack. In various embodiments, this includes stacking the battery anode with additional battery anodes. In further embodiments, this includes stacking cathodes with the battery anode.

Various embodiments of the present subject matter dispose the battery stack into a battery case. In various embodiments, the battery case has at least one feedthrough. In some embodiments, a first terminal connected to the battery stack through the at least one feedthrough. Various embodiments additionally fill the battery case with an electrolyte. In various embodiments, the electrolyte is an organic compound.

Various embodiments additionally include positioning the battery case, along with pulse generation electronics connected to the battery case, into a hermetically sealed housing having a first opening sized for passage of the battery case and pulse generation electronics, with a housing lid sealably conformed to the first opening.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover adaptations or variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive. Combinations of the above embodiments, and other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the present subject matter should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.